Susan Powell's husband and his family have worked with "six law-enforcement agencies" to find her, according to her father-in-law.

Steve Powell, Josh Powell's father, also offered a theory about what happened to his daughter-in-law.

"Some credible insiders involved in the investigation have stated to us that they believe she is alive and may have left of her own accord," Steve Powell wrote in an e-mail to The Tribune .

Josh Powell and his family have said little publicly since Susan Powell disappeared about six months ago.

"We know the general public has some legitimate questions, even if we don't always feel at liberty to respond to everything," Steve Powell wrote. "But we also feel that a lot of the questions coming from a core group of detractors are asked rhetorically and are designed to raise doubts about our family."

"When you read the blogs and articles," Steve Powell added, "you notice that those motivations revolve heavily around a religious disagreement."

Susan Powell disappeared Dec. 7 from her West Valley City home. Her husband, Josh Powell, has said he took his young sons on a late-night camping trip to Simpson Springs in Tooele County and when he returned his wife was gone.

Josh Powell gave some early interviews to West Valley City police but has not responded to requests to speak with detectives there again. West Valley City police have called him the only person of interest in his wife's disappearance.

In his e-mails to the newspaper, Steve Powell did not specify what law-enforcement agencies he and his son have been working with or how they have attempted to find Susan Powell.

"The agencies we are working with don't want or need the publicity," he wrote.

Later in the e-mail, he added: "We have worked with six law-enforcement agencies so far, who are involved in our efforts to find Susan."

West Valley City police Capt. Tom McLachlan on Wednesday said he is not aware of the agencies with which Josh Powell has reportedly worked.

"I guess you can say he's talked to us," McLachlan said, who added his department has a standing invitation for Josh Powell to submit to another interview.

In February, SusanPowell.org was launched. It asks for help in locating the missing woman and refers to Josh Powell as a loving father and husband. Although the posts on the site are unsigned, Steve Powell confirmed the site "belongs to us, and a number of friends and family members have contributed."

A post dated Sunday says Susan Powell's father, Chuck Cox, has used the "Mormon Church phone directory" to call Josh Powell's friends and to "pressure" him. The post also accused people of being hostile to Josh Powell for moving in with his father, who is a former member of the church.

Steve Powell said: "I've taken a look at a few blog posts [Tuesday] and it looks like people feel like we are attacking their religious views. If you read the page carefully, you will notice that this is not the case. We have not mentioned one tenet of Mormonism, and there's no gratuitous negativity."

Shelby Gifford, a spokesman for the Cox family, on Monday said Chuck Cox has not used any church directory to pressure Josh Powell, though Cox has repeatedly asked his son-in-law to cooperate in the police investigation.

"If Josh is feeling this huge sense of pressure, the best way to relieve it is to sit down with police," Gifford said.

When asked about Susan and Josh Powell's sons, ages 5 and 3, Steve Powell said his family has consulted a child psychologist and implemented the advice.

"They are very happy and well-adjusted, although they miss their mother," Steve Powell wrote. "They know their mommy and daddy both love them."

A spokeswoman for Susan Powell's parents said billboards promoting the search for the missing woman will soon be going up. Shelby Gifford said the billboards will be in Salt Lake County and in Puyallup, Wash., where Susan and Josh Powell are from and where Josh Powell now resides.

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